1. Field of the Invention
The present invention relates to wireless communications and more particularly to fixed wireless access communication systems.
2. Description of Related Art
Radio communication devices are often being used along with or in replacement of conventional wireline telephone systems. These radio communication devices provide many advantages over wireline systems. One advantage relates to the supporting infrastructure. Radio communication systems are simpler and less expensive to deploy in comparison to conventional wireline systems. Additionally, radio communication systems often have lower maintenance costs. Finally, radio communication systems are economically feasible in those sparse areas where low demand for communication services does not justify the cost of installing a wireline network.
In a fixed wireless access system (FWA), base stations form an interface between conventional wireline networks and wireless subscriber units. A subscriber unit is a user device which contains a radio transceiver for communicating with a base station. Subscriber units are often made to be compatible with ordinary wireline telephones. Typically, an ordinary telephone is plugged into the subscriber unit in place of a standard telephone wall jack such as an RJ-11 jack. The base stations within an FWA are geographically placed at intervals so as to be within range of select subscriber units. The service area of a base station is known as a cell or cell area. Subscribers to fixed wireless access systems typically are served by one cell in an FWA network (hereinafter, "primary cell").
Typically, a border cell subscriber unit will "lock onto" a cell's base station at power up after determining that the base stations control channel signal strength is stronger than that of other neighboring cell base stations. Once a subscriber unit responds to a control channel transmission, that cell becomes the primary cell. More specifically, the subscriber unit's directory number is assigned within an FWA controller to a single cell area (the primary cell) served by a specified base station. The operation and use of control channels as described is known to those skilled in the art. Thereafter, a FWA controller examines a subscriber list of directory numbers when it receives an indication that a wireless transceiver within its cell is trying to originate a call through the fixed wireless access system. The controller examines this subscriber list to determine that a proper subscriber is attempting to place a call. If the identification signals transmitted by the transceiver do not correspond with a directory number within this subscriber list, the call request is not processed. For calls which are being received by a switch for a specified FWA subscriber unit, the switch typically transmits a signal to a specified mode in an FWA controller to prompt it to issue page request signals to a base station to complete the call to the specified FWA controller unit.
This arrangement works well in the FWA system so long as a subscriber is not a border cell subscriber. A border cell subscriber is a subscriber of the FWA system services whose geographic placement is the fringe or border of a cell area. Border cell subscribers characteristically tend to receive weaker signals from the serving base station. On occasion, border cell subscribers cannot receive or initiate calls because random interference prevents the ability of base station of the primary cell and the border cell subscriber to complete a connection.